The present invention relates generally to a process for manufacturing a multilayer composite acoustical and thermal insulator which may be utilized to insulate an environment such as a passenger compartment of a vehicle from the heat and sound generated by mechanical components of that vehicle during its operation. Further uses include application in insulating appliances such as dishwashers and clothes driers and providing sound and thermal insulation for buildings including homes, offices and industrial structures.
It is well known in the art to provide acoustical and thermal insulators on an automobile, truck or other vehicle in an effort to protect and insulate the operating or passenger compartment from the noise and heat generated by the mechanical equipment of the associated vehicle. Toward this end, mats of high temperature glass fibers have been utilized, eg. (a) on the fire wall between the dashboard and engine compartment and (b) along the floor pan of the vehicle between the passenger compartment and the drive line and exhaust system. These materials provide heat insulation which makes it possible to maintain cooler and more comfortable temperatures in the operator/passenger compartment particularly during the summer months. Additionally, these materials provide needed sound insulation, reducing or eliminating various mechanical sounds of the motor, drive train as well as the suspension and tires as the vehicle travels over the often rough and bumpy surface of the roadway.
Various methods of manufacturing or fabricating such acoustical and thermal insulators are known in the art. Examples of these methods are found, for example, in U.S. Pat. Nos. 5,055,341 to Yamaji et al. and 5,501,898 to Fottinger et al.
In the Yamaji et al. patent, woven and/or non-woven fabrics are laminated to a composite of fibers and thermal plastic resin. In the Fottinger et al. patent, a multilayer, multi-density composite is disclosed incorporating polyester fibers. The fibers are preheated in a furnace by metal plates above the melting point of the fibers. The non-woven fabric fiber layers are loaded into a molding tool and exposed to molding pressure for a dwell time sufficient to complete the molding process. The part is then cooled below the softening temperature of the fibers to set the composite in the final molded shape.
While various processes are known in the art for constructing an effective insulator, a need still exists in the art for (a) insulators providing still more enhanced acoustical and thermal insulating properties as well as (b) more reliable and economical processes for manufacturing such insulators.
In accordance with the purposes of the present invention as described herein, an improved process for manufacturing or fabricating an acoustical and thermal insulator of enhanced performance characteristics is provided. The novel process comprises the steps of forming an insulator precursor by orienting an insulation insert in a desired location between a first facing layer and a polymer based blanket layer, applying differential heat to two opposing sides of the insulator precursor and applying pressure to the insulator precursor. In this manner, the insulator precursor is molded to a desired shape while also providing the polymer based blanket layer with a first zone of relatively high density adjacent a warmer of the two opposing sides and a second zone of relatively low density adjacent a cooler of the two opposing sides. The molding process is completed by cooling the molded precursor to set the insulator in the desired shape with the first zone having a first density A and the second zone having a second density B where A greater than B.
The insulator precursor may be formed in a continuous operation from continuous webs of starting materials. Alternatively, the process may include the step of cutting the heat reflective material and polymer based blanket material along with the insulation insert to desired dimensions prior to the forming step.
The differential heat and pressure are applied to the insulator precursor by first and second molding elements (eg. platens, rollers). More specifically, the first molding element is heated to provide a first temperature in the first or high density zone above a softening temperature to characteristic of the polymer blanket material being processed and a second temperature in the second or low density zone below the softening temperature characteristic of the polymer blanket material being processed. Typically, the first temperature is between 200-400xc2x0 F. and more typically between 200-275xc2x0 F.
The pressure is applied at a level between substantially 0.5-100.0 psi for approximately 10-90 seconds and more typically approximately 15-45 seconds dwell time. Further, the method includes the compressing of the insulator precursor between approximately 10-95% and more typically 50-90% when applying the pressure in order to complete the molding process.
In accordance with yet another aspect of the present invention, the process for forming a multilayer composite insulator comprises the steps of forming an insulator precursor by orienting an insulation insert in a desired location between a first facing layer and a first and second layer of a polymer based blanket material, applying heat to two opposing sides of the insulator precursor and applying pressure to the insulator precursor so that the applied heat and applied pressure mold the insulator precursor to a desired shape. This is done to provide a first zone of relatively high density in the first layer of the polymer based blanket material and a second zone of relatively low density in the second layer of the polymer based blanket material. The process further includes the cooling of the molded precursor to set the insulator in the desired shape. Advantageously, the present process allows one to reliably and efficiently form a multilayer, multidenisity composite insulator of enhanced acoustical and/or thermal insulating properties at a reduced overall cost.
They also may have the same or different softening temperatures. If the layers have different softening temperatures, the first layer softening temperature C is typically less than the second softening temperature D.
In this process, differential heating may be utilized to heat the first and second zones. Specifically, the first molding element is heated to provide a first temperature in the first zone above a first softening temperature characteristic of the first layer of polymer based blanket material and a second temperature in a second zone below a second softening temperature characteristic of the second layer of polymer based blanket material.
The first temperature is typically between about 200-400xc2x0 F. and still more typically between about 300-375xc2x0 F. Pressure is applied at a level between substantially 0.5-100.0 psi typically for approximately 5-45 and more typically 5-20 seconds. The insulator precursor is compressed between about 50-95% and more typically between 75-90%.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described preferred embodiments of this invention, simply by way of illustration of several of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded s illustrative in nature and not as restrictive.